Apparatus for making finned tubing



Oct. 16, 5 QR APPARATUS FOR MAKING FINNED TUBING 3 Sheets-Sheet 1 Filed Dec. 14. 1948 INVENTOR ERNEST BRUEGGER wmmmfl 0mm FW/W2 2 ATTORISES Oct. 16, 1956 BRUEGGER APPARATUS FOR MAKING FINNED TUBING Filed Dec. 14, 1948 3 Sheets-Sheet 2 INVENTOR ERNEST BRUEGGER fl rfimiwum ATTORNEYS BY kid/WM Oct. 16, 1956 E. BRUEGGER APPARATUS FOR MAKING FINNEID meme 3 Sheets-Sheet 3 Filed Dec. 14, 1948 INVENTOR ERNEST BRUEGGER ATTORNEYS United States Patent 2,766,805 APPARATUS FOR MAKING FINNED TUBING Ernest Bruegger, Massillon, Ohio, assignor to The Griscom Russell Company, New York, N. Y., a corporation of Delaware Application December 14, 1948, Serial No. 65,174 3 Claims. (CI. 15.3-64.5)

This invention relates to improvements in finned tubing andto methods for manufacturing the same.

The primary object of my invention is to increase the area of extended surface of a finned heat transfer tube in proportion to the length and diameter of thetubing to a greater extent that has heretofore been obtained.

In recent years the use of heat transfer tubes having extended surfaces in the form of helically wound fins has extended into many fields, and in many instances it is desirable to provide as great an extended surface as possible with respect to the length of the tubing.

By means of the invention disclosed in the accompanying specification I am able to increase the fin area per unit of length and diameter to more than twice what't'o my knowledge has been possible by processes heretofore used. It has heretofore been the practice in the manu facture of tubing with helically wound fins to form a helical groove in the surface of the tube and then, after the edge of the fin is seated in the tube, compress the' metal of the tube against the base of the fin by meansof knurling rollers. In this process, however, the space between the successive turns of the fin must exceed the,

thickness of the knurling roller for compressing the metalon the inside of the fin against the base of the fin; Also in the old process the width or height of the fin with relation to the diameter of the tube to which it is to be applied is limited for the reason thatthe edge of the fin to be seated in the preformed groove in the tube must be sub stantially flat, that is, without corrugations around itsinside diameter, and a thin ribbon of metal of substantial width cannot be readily coiled into a close helix of corn-' paratively small diameter without forming the surplus metal around the inner diameter of the helix into corrugations. H H

In carrying out the invention of this application I precoil a wide ribbon of thin metal, for example co'ppe'r, into a closely coiled helix of a diameter to fit the tube, forming during the coiling operations corrugations in the edge" of the metal at the inner diameter of the" helix. The: length of ribbon soprecoiled is assembled on the tubewhich has not previously been grooved, and the leading end of the ribbon is soldered to the tube. The tube is rotated and the fin applying mechanism is advanced lon-= gitudinally of the tube at a. rate such that the relativemovement of the tube and fin applying. mechanism at each revolution is equal. to the desired spacing between the coils of the helix. This distance may be very short, as there is no roller engaging the metal of the tubebetweerr the turns of the fin as in the above-described process: Instead; inaccordance with my improved method, the only part of the machine which enters between adjacent turns of the helixlis a thin steel backing plate having. a. flat face engaging the inner face of the fin and" against which the corrugations in the metal: at the base of the firr' are flattened" by means of pressurerollers engaging the opposite face of the fin, as the corrugations are flattened thetinner. edge of thefin is worked into the metal of the tube to thereby produce a good heat transfer connection between the fin and the tube. By means of the improved method herein disclosed, fins over one-half inch. in height and twenty-four turns to the inch have successfully been applied to tubes no greater than three-quarters of an inch in diameter.

In the accompanying drawings I have illustrated a preferred form of apparatus for manufacturing my improved type of finned tubing, and have illustrated the successive steps employed in such manufacturing operation.

In said drawings:

Fig. 1 is a perspective view showing the ribbon of which the fin is formed, precoiled for assembly on the tube;

Fig. 2 is a perspective view of a short section of the finished tube;

Fig. 3 is a detail view showing the action on the fin during its application to the tube;

Figs. 4, 5 and 6 are detail views 'on an enlarged scale showing the successive changes in the metal at the base of the fin during the application of the fin to the tube;

Fig. 7 is a plan view of the fin-applying apparatus;

Fig. 8 is an end elevation of the mechanism shown in Fig. 7;

Fig. 9 is a sectional view on an enlarged scale on line 99 of Fig. 7.

Fig. 10 is a sectional view on an enlarged scale on line 10-10 of Figs. 8 and 9; and

Fig. 11 is a sectional view on an enlarged scale on line 1111 of Figs. 8 and 9.

Referring to the drawings, the tube 1 is supported by any suitable means, and is continuously rotated during the application of the fin. For example, the tube may be held in the chuck of a lathe having the usual carriage supported on the machine bed beneath the tube for movement back and forth in a direction parallel with the axis of the mandrel these parts are of usual construction and are not illustrated.

The ribbon of metal forming the fin is pre-coiled in the form of a closely wound helix as shown in Fig. l. The ribbon is preferably of thin metal and the width of the ribbon is so great in proportion to the diameter of the helix that the metal of the ribbon along the inner edge of the helix is corrugated in the pre-coiling operation, the corrugations 2 being approximately of the configuration shown in Fig. 1.

The mechanism for applying the fin to the tube to provide a good heat-conducting contact is carried by a base 3 mounted on the carriage which extends across the ma chine beneath the tube. Supported on the base 3 on one side of the tube is a circular plate 5, which may be adjusted to various angular positions about its center in accordance with the desired pitch of the fin. v A clamp 6 is attached to the plate 5 and mounted in the clamp is a head 7 carrying the fin-applying instrumentalities.

The fin applying mechanism comprises a pair of rollers 3 of the shape illustrated in "Figs. 7 and 10. That is to say, the rollers are fiat on one face 9 and are tapered on the other face it) and have a hollow spindle 11 projecting from the face 10. The spindle 11 is supported for rotation in a stationary bushing 12. The bushing in turn is mounted on the head 7 by means of a bracket 13 which is adjustable toward and away from the tube.

The fiat faces 9 of the rollersengage the outer face of the ribbon, that is, the face toward the unattached portion of the pro-coiled ribbon.

Supported in the hollow bearing 11 of the roller 8 for rotation independently of the roller 8 is a grooved roller 14 which is partially seated in a recess in the fiat face 9 of the roller 8, the recess being of a depth such that the adjacent face of the groove in the roller 14 lies in the same plane as the face 9 of roller 8. The groove in the roller 14 fits over the outer edge of the fin and the rollers 8 and 14 are of such a size that when the bracket 13 is adjusted toward the tube to a position where the grooved roller 14 presses the inner edge of the fin hard against the tube, the periphery of the rollers 8 Will be pressed hard against the surface of the tube. Preferably the circumference of the rollers 8 is knurled as shown so that the rotation of the tube will rotate the rollers 8 and the surface of the tube between the fins will be roughened.

Supported on the head '7 opposite the face 9 of the rollers 8 is a block 15. The block 15 is recessed opposite the rollers 14 so that it may be spaced from the face 9 of the rollers 8 a distance just slightly greater than the thickness of the ribbon from which the fin is formed. The edge of theblocklS toward the tube is provided on the side of the face away from the rollers 8 with a semicircular recess 17 of a diameter slightly greater than the outer diameter of the wound fin, the depth of the recess being such as to provide a thin plate-like extension 18 (see Fig. 11) of a thickness slightly less than the spacing between the fins of the finished tube. This extension 18 of the block 15 is provided on its inner edge with a semicircular recess of a diameter slightly greater than the inside diameter of the tube. The extension 18 thus provides a backing against the outer face of the fin, that is, the face opposite the rollers 8 extending approximately 180 around the circumference of the tube, with the space between the extension 18 and the flat face 9 of the rollers 8 just su-tficient for the fiat outer portion of the fin to pass freely through it.

Mounted on the frame of the machine opposite the head 7 is a second support 20 similar to the plate and likewise mounted for angular adjustment with respect to the axis of the tube. Plate 20 carries a bracket 21 in which is supported for adjustment toward and from the tube a head 22 upon which is mounted a pressure roller or disk 23 so positioned that its periphery engages the tube at a point which is in the same vertical plane as the points of engagement of the two rollers 8. The roller 23 thus serves as a backing roller to prevent lateral movement of the tube under the pressure exerted by the rollers 8 and 14 on the opposite side of the tube.

In operation the leading end of the pre-coiled fin is attached to the tube by a drop of solder 24, as shown in Fig. 7. The tube is then adjusted in the machine so that the extension 18 engages the face of the fin on its exposed side adjacent the point of attachment, while the flat face 9 of the rollers 8 engages the opposite face of the fin and the grooved rollers 14 press against the edge of the fin. The pressure roller 23 is then adjusted against the opposite face of the tube, the three rollers forming a 3-point support for the tube for rotation concentric with its axis.

As the tube with the attached fin is rotated, the flat face 9 of the rollers 8 presses the fin against the backing plate 18 and simultaneously flattens the corrugations at the inner edge of the pre-coiled fin, the operation being illustrated in Figs. 3, 4, 5 and 6. In flattening the corrugations as illustrated in Figs. 3, 4, 5 and 6, the metal of the fin at the crown of the corrugations is forced into the radial plane of the main body of the fin and is thereby worked into the metal of the tube in a manner to produce an excellent heat-conducting contact between the tube and the fin. As the corrugations extend in both directions from the plane of the fiat exterior portion of the fin, the metal forming the crowns of the corrugations on the opposite sides is pressed into the metal of the fin from opposite directions, thereby positively locking the fin to the tube against longitudinal displacement in either direction. If the metal of the tube is substantially harder than the metal of the fin, the inner edges of the corrugations of the fin will be flattened out or compressed against the wall of the tube, but in this instance also the fin is firmly locked against longitudinal movement of the tube for the reason that movement of the fin longitudinally with respect to the tube in either direction tends to further compress the metal of the corrugations on the face of the fin in a direction toward which the longitudinal displacement is eifected, thus increasing the friction between the tube and the base of the fin.

By my improved process a finned tube may be produced with wide fins so closely spaced as to increase the heat radiating surface of the tube to a much greater extent than can be obtained by the processes now employed. In a tube of the dimensions given above, the fin surface is more than twenty times the area of the base tube.

While I have illustrated in the accompanying drawings an apparatus which has been found satisfactory for the commercial production of my improved heat radiating tube, it is to be understood that the invention is not limited to the apparatus disclosed. For example, the fin need not be pre-coiled in the manner shown but may be coiled as it is applied to the tube. It is also not necessary to use the backing plate opposite the pressure rollers although it is desirable in order to flatten the corrugations on both sides of the fin. It is also to be understood thatof said tube approximately equal to the radius of the tube and the width of the fin to be applied whereby the roller engages the edge of the fin, a backing plate carried by said support and positioned to project between the fin engaged by said roller and the previously applied adjacent fin, and a second roller carried by said support in position to engage the wall of the tube on the side of the fin away from said backing plate, and means carried by said support for preventing lateral displacement of said tube during the finning operation.

2. An apparatus for making finned tubing wherein a tube is supported for relative axial and rotary movement with respect to a fin applying mechanism, said fin applying mechanism comprising a frame a support thereon spaced from the axis of the tube, a roller carried by said support with its periphery positioned at a distance from the axis of said tube approximately equal to the radius of the tube and the width of the fin to be applied whereby the roller engages the edge of the fin, a backing plate carried by said support and positioned to project between the fin engaged by said roller and the previously applied adjacent fin, and a second roller mounted on said support concentric with the first roller and having one face normal to its axis of rotation and positioned to contact the face of the fin at the location where the fin is held against the tube by the first mentioned roller and a third roller carried by said support in position to engage the wall of the tube on the side of the fin away from said backing plate, and means carried by said frame for preventing lateral displacement of said tube during the finning operation.

3. An apparatus for making finned tubing wherein a tube is supported for relative axial and rotary movement with respect to a fin applying mechanism, said fin applying mechanism comprising a frame a support thereon spaced from the axis of the tube, a roller carried by said support with its periphery positioned at a distance from the axis of said tube approximately equal to the radius of the tube and the width of the fin to be applied whereby the roller engages the edge of the fin, a backing plate carried by said support and positioned to project between the fin engaged by said roller and the previously applied adjacent fin, and a second roller mounted on said support concentric with the first roller and having one face normal to its axis of rotation and positioned to contact the face of the fin at the location where the fin is held against the tube by the first mentioned roller, said second roller being of a diameter to 5 engage the wall of the tube at the base of said fin, and

a third roller carried by said support in position to engage the wall of the tube on the side of the fin away from said backing plate, and means carried by said frame for preventing lateral displacement of said tube during 10 the finning operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,840,317 Horvath Ian. 12, 1932 15 6 Berg June 14, 1932 Berg June 20, 1933 Owston Mar. 13, 1934 Dewald Feb. 26, 1935 Berg Mar. 28, 1939 Lea Mar. 19, 1946 Lea Feb. 28, 1950 FOREIGN PATENTS Germany Mar. 30, 1925 Germany Aug. 10, 1932 

